Means for regulating power for pumps

ABSTRACT

Means for additive power regulation for at least two pumps comprising a control conduit which is connected to the main pump conduits and is provided with throttle means so adjusted to the volume-flows of the pumps that a pressure set up in the control conduit will be proportional to the sum of the effects of the pumps, said pressure actuating regulating means for connecting the main flow from one of the pumps to the main flow to the other pump.

United States Patent 15] 3,695,783 Soyland et a1. Oct. 3, 1972 MEANS FOR REGULATING POWER 2,823,518 2/1958 Murray ..137/567 FOR PUMPS 2,965,036 12/1960 Wood ..4l7/62 In o s: Kristian Budzlch both of 4340 Bryne, Norway 2,870,776 l/ 1959 Marsh ..417/286 3,431,856 3/1969 Whitmore et al ..417/216 Flled! 1970 3,526,468 1/ 1970 Moon et a1. ..417/216 [21] App]. No.: 86,412

Primary Examiner-Wil1iam L. Freeh Att H l & St [30] Foreign Application Priority Data army 0 man em Dec. 3, 1969 Norway ..4777 ABSTRACT Means for additive power regulation for at least two 51.3.51 ..417/2lF664;Z/92/(8)g pumps comprising a control conduit which is com [58] Field 137/5 nected to the main pump conduits and is provided 137 with throttle means so adjusted to the volume-flows of I the pumps that a pressure set up in the control conduit will be proportional to the sum of the effects of the [56] References C'ted pumps, said pressure actuating regulating means for UNITED STATES PATENTS clonnectin the mfiiin fLow from one of the pumps to t t t t 2,599,701 6/1952 Eames ..4l7/62 e mam ow o e 0 er pump 2,655,109 10/1953 Walker ..417/286 3 Claims, 2 Drawing Figures MEANS FOR REGULATING POWER FOR'PUMPS BACKGROUND OF THE INVENTION The present invention relates to a means for summation of the power from two or more pumps operated by a common motor. The pumps may be either constant volume-flow pumps or variable-volume flow pumps.

It is known that by using variable volume-flow pumps the power take-off can be regulated by decreasing the volume-flow by degrees as the pressure requirement-increases. In this manner it is possible, when idling or when the power requirement is slight, to achieve rapid movement without thereby requiring a relatively large prime mover. This'has not previously been possible when using constant volume-flow pumps for power transmission. The object of the present invention is to provide a means which, in'a simple manner, permits use of constant volume-flow at low pressure and less volume-flow at higher pressure.

The advantage of power regulated pumps in for example, digging machines, loading machines and the like, is the improved utilization of the effect of the prime mover. It is possible to achieve greater velocities when idling, and with small loads, with a relatively small power motor. Without power regulation, the power motor must be dimensioned such as to' have sufficient power to operate the pump (or pumps) at maximum volume-flow and maximum pressure. This entails utilization of the power motor only in cases where the working members require maximum pressure. When the working members require low. pressure, the motor is only partially loaded and thus, in effect, over dimenv sioned.

At the present time, power regulated pumps are utilized in the main only in systems which operate with relatively high pressure, since these units are constructed for systems where relatively little volume flow is used. Variable volume-flow pumps are comparatively expensive and thereby .uneconomical with greater volume-flows and low working pressure. In systems with relatively low working'pressure, it is therefore desirable to utilize less expensive pump-units such as gear wheel pumps, blade pumps or the like. Notwithstanding, the disadvantage has been as described hereinbefore, thatthis type of pump requires greater maximum effect from the power motorl SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view illustrating one embodiment of the invention, and

FIG. 2 is a similar view of a second embodiment.

FIG. 1 shows a system having two constant volumeflow pumps which supply a pressure medium to two separate connections. The pumps are operated by a common motor M with a determined effect-E. In'the example shown, pumps of different sizes are selected, in which pump PF] is larger than pump PF2. As will be apparent from the further description, this is necessary if both service circuits are to receive pressure medium after the regulation is carried out.

The main circuits, as shown in Fig. l, are constructed in the well-known mannerin whichthe pumps PFl AND PF2 supply medium from atank 3 through suction conduits 4, 7.'The pressure medium flows further through pressure conduits 5, 9 to distribution'valves l and 2. When the distribution valves are not being operated, and are thusin neutral position, the medium flows to the tankvia-a returnconduit '6. When the distribution valves-are operated to one or other end position, the pressure medium flows to consumers A and B, and, from the consumers, returns to the tank 3.

valve which, in an inoperative state, closes the communication between the conduits l0 and 12. The valve has a hydraulic operation unit 17 which, on supply of pressure medium, opens the valve againsta spring 18. The spring force may be adjusted by means of an adjusting screw-19,'so that the valve opens-at a determined'pressure In the system shown in'Fig. 1, pressure will arise in conduits 5 and -9 when the valves are operated so that the consumers carry out the work. If the conduits 5 and 9 contain unequalpressure, a pressure'medium flow through control conduit 13 and the throttles l4 and 15 -will takeplacei-Pressuredrop thus occurs overthese throttles. The relation between these throttles 14 and 15 is determined so that the pressure arising in conduit 16 represents the common effect of the pumps Pfl and H2. If the volume-flow of the pumps PF 1 and PF2 is signified by Q1 and Q2 respectively, and the pressure P1 and P2 respectively, the following equation is achieved where Ps is the pressure arising in the conduit 16.

On correct relation between thethrottles 14 and15, the pressure'Ps will be constant as long as the sum of the effect from the pumps PF 1 andPF2 is constant. The total effect from both pumps may'then be expressed as:

where E is the effect expressed in horsepower and K is a constant factor.

In general,-it is desirable that the regulation occurs when the'power-take-ofi'is equal'to'the maximum effect of the power motor. The control pressure for maximum effect is determined from E max The valve 11 is adjusted to switch at apressure in the conduit 16 which is equal to Psr. The adjustment is undertaken by adjusting the force of spring 18 by means of adjusting screw 19.

The switching over of the valve 11 allows communication between the conduits 10 and 12 so that pressure medium from conduit 5 flows over to suction conduit 7. The one-way valve 8 prevents the pressure medium from flowing back to the tank 3. The pump PF2 has thereby a feed pressure (suction pressure) equal to the pressure in theconduit 5. The power requirementof pump PF 2 is thereby reduced to The total power requirement for both pumps after regulation beingthereby The flow of pressure medium to the valve 1 is now reduced to (Q1 Q2) while the flow of medium to valve 2 remains the same as before. The working pressure may now be increased further until maximum motor effect is achieved.

The volume-flow in the control conduit 13 is relatively small since the through-flow areas in the throttles l4 and 15 may be very small, usually less than 1 m/m in diameter. it will normally be possible to maintain the through-flow at below 3 percent. A loss of this size will be within the tolerance of the volume-flow of the pump. The one-way valve 8 is dimensioned so as to cause the least possible pressure drop between tank and pump.

When the pressures in the conduits drop so that the control pressure in the conduit 16 is below Psr, the valve 11 returns to neutral position and thereby closes communication between conduits l and 12.

The regulation may also be used to advantage for regulating variable volume-flow pumps as illustrated in Fig. 2. The figure shows a two-circuit system with two variable pumps PVl and Pv2. The progress of the pressure medium flow is, in general features, as previously described for Fig. 1.

The volume-flow from a variable pump may, as is known, be varied by altering the angle of the oblique plate (thrust plate) so that the length of the piston stroke is increased or decreased. In the present invention, the regulating member consists of a single-acting cylinder 20 and 21 for pumps PV] and PV2, respectively. A spring 22, 23 holds piston 24, 25 in a neutral position. The piston is in direct communication with the oblique plate of the pump via arm 26, 27. When the regulating cylinder is in a neutral position, the pump is adjusted to supply maximum volume-flow. When pressure arises in control conduit 28, 29, the force on pressure side 30, 31 of the piston 24, 25 will increase. When this force exceeds the spring force, the piston will move until there is balance between the spring force and pressure force. This movementis transmitted via arm 26, 27 to the oblique plate of the pump and adjusts the angle thereof;

The regulating pressure is produced in the same manner as described for Fig. 1. On operation of the distribution valves 1 and 2', pressure occurs in main conduits 32, 33 in accordance with the power requirement of the consumers A, B. This pressure is transmitted via the throttles 14' and to the control conduit 13.

When there is a pressure difference between the main conduit 32-and 33, flow will occur in the control con duit l3 and over the throttles l4 and 15. The throttles are adjusted so that the pressure occuring in conduit 13' is'a measure of the total power from the pumps PVl and PV2. The control pressure in the conduit 13' lzg'anatssz a an ir ttfirst? i?) 255%: adapted so as to adjust, at the control pressure prevailing at all times in the conduit 13', the volume-flow from the pumps so that the total effect thereof corresponds to the effect of the power motor. in this manner, a constant power regulation of variable pumps is achieved.

The regulating cylinders 20 and 21 are not directly included in the invention since they are of a type known per se.

In the examples a summation of the effects from two pumps is illustrated, it is, of course possible however, to summate the effects from more than two pumps. This may be done by first summating two pumps so that a common control pressure is achieved. The common control pressure is then summated with pressure from the third pump etc.

Having described our invention, we claim:

1. A hydraulic system for earth moving equipment for controlling at least two movable components thereof, including a separate circuit for each movable component, each circuit comprising a pump, a suction conduit between a source of hydraulic medium and the pump inlet, a pressure conduit between the pump outlet and the movable component, a return conduit between the movable component and the source, motor means for driving the pump, a regulating means for the pumps, said regulating means including a cross conduit providing communication between the pressure conduits downstream of the pump outlets, throttles for the cross conduit, a regulating component, and a control conduit providing communication between the cross conduit intermediate the throttles and the regulating component for operating the regulating component.

2. The hydraulic system as claimed in claim 1 in which each pump is a constant volume-flow pump and the regulating member is a hydraulically operated valve controlling conduits leading from the valve to the pressure conduit of one pump down-stream of the pump outlet and a second conduit leadingfrom the valve to the suction conduit of the other pump upstream of the pump inlet and a one-way valve in the suction conduit of the other pump to prevent the hydraulic medium flowing back to the source.

3. The hydraulic system as claimed in claim 1 in which said pumps are variable volume-flow pumps and the regulating component includes a single acting cylinder piston unit, spring means holding the piston in a neutral position, means directly connecting the piston with a thrust plate of the pump and a branch conduit leading from the control conduit to each cylinder. 

1. A hydraulic system for earth moving equipment for controlling at least two movable components thereof, including a separate circuit for each movable component, each circuit comprising a pump, a suction conduit between a source of hydraulic medium and the pump inlet, a pressure conduit between the pump outlet and the movable component, a return conduit between the movable component and the source, motor means for driving the pump, a regulating means for the pumps, said regulating means including a cross conduit providing communication between the pressure conduits downstream of the pump outlets, thRottles for the cross conduit, a regulating component, and a control conduit providing communication between the cross conduit intermediate the throttles and the regulating component for operating the regulating component.
 2. The hydraulic system as claimed in claim 1 in which each pump is a constant volume-flow pump and the regulating member is a hydraulically operated valve controlling conduits leading from the valve to the pressure conduit of one pump down-stream of the pump outlet and a second conduit leading from the valve to the suction conduit of the other pump upstream of the pump inlet and a one-way valve in the suction conduit of the other pump to prevent the hydraulic medium flowing back to the source.
 3. The hydraulic system as claimed in claim 1 in which said pumps are variable volume-flow pumps and the regulating component includes a single acting cylinder piston unit, spring means holding the piston in a neutral position, means directly connecting the piston with a thrust plate of the pump and a branch conduit leading from the control conduit to each cylinder. 